Sean Carroll is a physicist at Caltech. His research
includes theoretical physics and astrophysics, especially cosmology, field
theory, and gravitation. He has published several research papers dark matter
and dark energy, modified gravity, violations of Lorentz invariance, extra
dimensions, topological defects, cosmic microwave background anisotropies,
causality violation, black holes, and the cosmological constant problem.
He is currently focused on origin of the universe and the
arrow of time, including the roles of inflation, baby universes, and quantum
gravity. In his recent video by Techinsider, he explains what existed before
Big Bang and it actually means. So watch and learn: